nftables has two types of sets/maps, one where userspace defines the
name, and anonymous sets/maps, where userspace defines a template name.
For the latter, kernel requires presence of exactly one "%d".
nftables uses "__set%d" and "__map%d" for this. The kernel will
expand the format specifier and replaces it with the smallest unused
number.
As-is, userspace could define a template name that allows to move
the set name past the 256 bytes upperlimit (post-expansion).
I don't see how this could be a problem, but I would prefer if userspace
cannot do this, so add a limit of 16 bytes for the '%d' template name.
16 bytes is the old total upper limit for set names that existed when
nf_tables was merged initially.
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
net/netfilter/nf_tables_api.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 4b55533ce5ca..02f45424644b 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -24,6 +24,7 @@
#include <net/sock.h>
#define NFT_MODULE_AUTOLOAD_LIMIT (MODULE_NAME_LEN - sizeof("nft-expr-255-"))
+#define NFT_SET_MAX_ANONLEN 16
unsigned int nf_tables_net_id __read_mostly;
@@ -4413,6 +4414,9 @@ static int nf_tables_set_alloc_name(struct nft_ctx *ctx, struct nft_set *set,
if (p[1] != 'd' || strchr(p + 2, '%'))
return -EINVAL;
+ if (strnlen(name, NFT_SET_MAX_ANONLEN) >= NFT_SET_MAX_ANONLEN)
+ return -EINVAL;
+
inuse = (unsigned long *)get_zeroed_page(GFP_KERNEL);
if (inuse == NULL)
return -ENOMEM;
--
2.43.0
